Looks like my issue was probably not the same bug... someone told me that if your units are in the Disputed exit zone when it first appears, they will leave the map. The help file is ambiguous about how this works. I had thought they had to be carrying a square in order to be removed.

rohlfinator wrote:Looks like my issue was probably not the same bug... someone told me that if your units are in the Disputed exit zone when it first appears, they will leave the map.

That's right - if your units are in the exit zone when the boxes appear or on any turn after that they'll escape, regardless of whether they're carrying boxes. It isn't what you'd expect and I'm not sure if it's intended behaviour but for now you just need to plan around it. You can be in the exit zones before the boxes appear without a problem.